Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.
In New Radio (NR), ultra-reliable and low latency communications (URLLC) is supported for emerging applications that demands high requirements on end-to-end latency and reliability. A general URLLC reliability requirement for one transmission of a packet is 1-10−5 for 32 bytes with a user plane latency of 1 ms. For URLLC, the target for user plane latency should be 0.5 ms for uplink and 0.5 ms for downlink.
In downlink transmission, the user equipment (UE) may need to transmit a feedback indication (e.g., acknowledgement (ACK) or negative acknowledgement (NACK)) to indicate whether a downlink signal is successfully received or not. The network apparatus may have to re-transmit the downlink signal if an NACK is received from the UE. However, the network may misinterpret the feedback indication due to interferences or propagation errors. For example, the network apparatus may misinterpret the NACK as the ACK. This may impact the downlink reliability since the network apparatus may not re-transmit the downlink signal to UE. The UE may have no chances to receive the missed downlink signal.
Accordingly, how to avoid misinterpretation for the feedback indications may be important for downlink transmission. In order to facilitate downlink reliability, it is needed to provide proper mechanisms and coordination for transmitting the ACK and the NACK signals.